The goal of this project is to produce software systems (deliverables) that address questions in population kinetics, to make them available to individuals and organizations, and to maintain them once they are released. These deliverables will be designed and developed to IEEE standards using state-of-the-art computer science methods. The software systems will be developed incrementally, and will be modularized so they can be used by other software developers upon request. Release information and service support for the modules and algorithms will be developed as part of our dissemination package. Each system will be described in more detail below. Unlike the other project descriptions in this application, we will not follow the usual "specific aims -> background -> significance -> methods" paradigm. The reason is that the design and development of reliable software is a complex process.